Electron tube structures



Oct. 10, 1961 R. F. SPURCK ELECTRON TUBE STRUCTURES FIG.|

Filed June 22, 1959 FIG. 2

INVENTOR.

RlCHARD E SPURCK AGEN United States Patent 3,003,603 ELECTRON TUBE STRUCTURES Richard F. Spurck, Wilton, Coma, assignor to Machlett Laboratories, Incorporated, Sprlngdale, Conm, a corporation of Connecticut Filed June 22, 1959, Ser. No. 822,101 6 Claims. (Cl. 18936.5)

This invention relates to electron tubes embodying ceramic envelope structures and has particular reference to novel means in an electron tube for joining together metal and ceramic parts which may be subjected to varying thermal conditions during normal operation of the tube. a

One of the main problems associated with the manufacture of electron tubes embodying both metal and ceramic parts is that encountered in providing a satisfactory seal between parts having different coefficients of expansion whereby the parts will be allowed to expand and contract different respective amounts under, varying thermal conditions without damaging the seal. In tubes of conventional structure this problem is complicated by the necessity for providing a relatively expansive area of solder on each of the parts being joined in order to insure against voids such as might destroy the vacuum within the tube. 1 y

The present invention overcomes these problems by the provision of a seal which embodies an annular flexible metal sealing member having a substantially L-shaped cross-sectional configuration, one arm of which is soldered adjacent its end to a surface of one of the members. The other arm is similarly secured adjacent its end to the surface of a reduced portion of the second member and lies adjacent a circumferential groove into which the sealing member may move under the influence of pressures caused by thermal expansion of the parts of the device. Such a seal further allows the parts to be assembled one within the other and to be held in spaced apart relation so that each part may be permitted unhampered movement with respect to the other part without damage to the seal or fracture of the parts.

It is, therefore, one of the objects of this invention to provide, in an electron tube, a seal between metal and ceramic parts which will allow each part to expand and contract under varying thermal conditions according to its own particular inherent thermal expansion characterist-ics without interfering with the expansion and contraction of the other part and without damaging the seal or fracturing the parts.

Another object is to provide a seal of the above char acter which is shaped and designed to permit unhampered relative movements of the ceramic and metal parts with respect to'one another when the parts are subjected to varying thermal conditions.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing, wherein FIG. 1 is an elevational view, partly in axial section,

of an electron tube embodying the invention; and

FIG. 2 is an enlarged sectional view of a seal formed according to the invention.

Referring more particularly to the drawing, there is shown an electron tube which embodies an envelope 10 formed of metal portions and ceramic portions joined,

together by vacuum-tight seals so that the interior of the envelope may be evacuated by suitable pumping proc- .esses A central ceramic envelope 11 insulatingly separates a metal tubular cathode terminal 12 from a 3,003,603 Patented Oct. .10, 1961 2 metal ring-like grid terminal 13. Extending within the cathode terminal 12 is a metal heater terminal 14. Grid terminal 13, cathode terminal 12, and heater terminal 14 are all connected internally of the tube to respective electrodes which function in a normal manner not constituting an important part of this invention.

Extending from the opposite side of grid terminal 13 is a tubular ceramic envelope portion 15 which encloses the inner end of a metal anode block 16. Anode block 16 is an elongated metal member preferably of nickeliron alloy or other material having eflicient thermal conductivity and having a coefficient of expansion different than ceramic portion 15, the inner end 17 of the anode ,block 16 being maintained in predetermined spacedrelation to the other electrodes (not shown) within the envelope. The anode block 16, is of a length to extend outwardly beyond the end of the ceramic portion 15, the extension 18 thereof being of larger diameter than the reduced portion 17 which is located within and in spaced relation to the inner surface .of ceramic portion 15. Anode block 16 is bored throughout a major portion of its length so as to receive an exhaust tubulation 19 whereby the interior of the tube maybe evacuated, after which the outer end of the tubulation 19 is closed to maintain a vacuum within the tube.

The anode block 16 is attached to and supported by the ceramic en'velope portion 15, and to accomplish this in accordance with this invention there is provided an annular'metal sealing ring 20 which is of L-shaped cross section as shown clearly in FIG. 2. At the point where the reduced anode portion 17 is joined to enlarged portion 18 there is formed a shelf 21 upon which the inner flange 22 of ring 20 is located. The other flange 23 of 'ring 20 is joined to the outer surface of ceramic member 15 near the end thereof in such a manner that said end is maintained in spaced relation to flange 22. Enlarged anode portion 17 is provided with a circumferential slot 24 at its extreme end adjacent flange 22. Thus only a relatively small portion'of flange 22 is joined to shelf 21 while the remaining portion of flange 22 overlies slot 24. Likewise, a relatively small portion of flange 23 is joined to ceramic portion 15 while the remainder of theflange overlies the space between the end of the ceramic portion 15 and shelf21.

16 is formed of nickel-iron alloy and the ceramic portion- 15 is formed of fosterite, a sealing ring'20 of nickel-iron alloy may be joined by a solder of silver or copper or combination of the two.

During operation of the tube, the anode block 16 will normally become heated to a considerably greater extent than ceramic envelope portion 15. The coeflicients of expansionof parts 15 and 16 are quite different. fore, if parts 15 and 16 are joined directly to one another, upon expansion or contraction the joint therebetween may become ruptured or one of the parts may be damaged. Such damage to the seal or to the parts is overcome in the presently described structure since the ring 20 will, through its inherent flexibility characteristics, permit the parts to expand and contract different respective amounts without damaging the seal. Upon expan- Theresion and contraction of the anode block 16, for example, the anode may be permitted to move toward or away from ceramic part 15 by reason of the flexibility of the portion of flange 23 which extends beyond the end of part 15. Likewise, longitudinal movement of the anode during expansion and contraction will be permitted by reason of the fact that flange 22 of ring 20 will flex, with such movement of the anode, toward and away from the adjacent end of member 15.

It will be noted that when the enlarged portion 18 of the anode moves toward ceramic member 15, the portion of the flange 22 which overlies slot 24 will tend to move freely and unrestrictedly into the slot. Thus there is no restraint upon the anode such as might tend to rupture the bonds between flange 22 and shelf 21 or between flange 23 and ceramic member 15.

While there is shown and described a preferred embodiment of the invention, it is to be understood that certain modifications in the structure may be made by those skilled in the art without departing from the spirit of the invention as expressed in the accompanying claims.

I claim:

1. An electron tube having an envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including a cylindrical metal member and a cylindrical ceramic member, the first of said members having a circumferential shelf-like surface facing one end of the second member, which shelf-like surface is spaced inwardly from a projected continuation of the outer surface of the first member by a circumferential recess in said outer surface, and flexible vacuum-tight seal means for joining the members together in spaced relation comprising an annular sealing member having a first flange bonded to the second member and having a second flange bonded to said shelf-like surface, the second flange being spaced from the adjacent end of the second member and having a portion overlying said circumferential recess in the outer surface of the first member, and the first flange having a portion overlying the space between the end of the second member and the adjacent surface of the second flange, said portions of the flanges being flexible whereby they may move freely into and out of said recess and space under the influence of expansion and contraction pressures caused by varying thermal conditions.

2. An electron tube having an envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including a ceramic member and a metal member, one of said members having an outer surface and having a shelf-like surface facing one end of the second member and further having a circumferential groove in the edge of said outer surface adjacent said shelf-like surface whereby the shelf-like surface is inset with respect to said outer surface, and flexible vacuum-tight seal means for joining said members together in spaced relation comprising a flexible sealing member having a first flange bonded to the second member and having a second flange extending parallel with and bonded to the shelf-like surface of the first member throughout the length of said shelf-like surface, the second flange having a portion overlying and movable with respect to said groove, and the first flange having a portion overlying and movable with respect to a space between the end of the second member and the adjacent surface .of the second flange.

3. An electron tube havingan envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including an annular ceramic member and an annular metal member, one of said members lying within the other member and of a length to extend outwardly beyond one end thereof, the

portion of the inner member which extends beyond the end of the outer member having a diameter at its end adjacent the end of the outer member which is larger than the diameter of the portion lying .within the outer member, the junction of said portions of large and small diameter providing an annular shelf near and spaced from the end of the outer member, a peripheral groove in said portion of largest diameter adjacent said shelf whereby the width of the shelf is reduced, and a vacuumtight seal means for joining said members together in spaced relation comprising a flexible sealing member having a first flange bonded to the outer surface of the outer member and having an inwardly directed second flange bonded to the shelf, the second flange having a portion overlying the groove, and the first flange having a portion overlying the space between the end of the outer member and the adjacent surface of the second flange.

4. An electron tube having an envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including a ceramic member, a metal member having a shelf-life surface facing one end of the ceramic member, which shelf-like surface is spaced longitudinally from the end of the ceramic member and is spaced inwardly from a projected continuation of the outer surface of the metal member by a recess in said outer surface, and flexible vacuum-tight seal means for joining the members together in spaced relation comprising a sealing member having a first flange bonded to the outer surface of the ceramic member and having a second flange bonded to said shelf-like surface, the second flange being spaced from the adjacent end of the ceramic member and having a portion overlying said recess, and the first flange having a portion overlying the space between the end of the ceramic member and the adjacent surface of the second flange, said portions of the flanges being flexible whereby they may move freely into and out of said recess and space under the influence of expansion and contraction pressures caused by varying thermal conditions.

5. An electron tube having an envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including a ceramic member, a metal member having an outer surface and having a shelf-like surface spaced from and facing one end of the ceramic member and further having a groove in the edge of said outer surface adjacent said shelf-like surface whereby the shelf-like surface is inset with respect to said outer surface, and flexible vacuum-tight seal means for joining said members together in spaced relation comprising a flexible sealing member having a first flange bonded to the outer surface of the ceramic member and having a second flange bonded to the shelf-like surface of the metal member throughout the length of said shelflike surface, the second flange having a portion overlying and movable into and out of said groove, and the first flange having a portion overlying and movable into and out of a space between the end of the ceramic member and the adjacent surface of the second flange.

6. An electron tube having an envelope comprising a plurality of elements connected together to enclose an evacuated space, said elements including an annular ceramic member and an annular metal member, the metal member lying within the ceramic member and of a length to extend outwardly beyond one end thereof, the portion of the metal member which extends beyond the end of the ceramic member having a diameter at its end adjacent the end of the ceramic member which is larger than the diameter of the portion lying within the ceramic member, the junction of said portions of large and small diameter providing an annular shelf near and spaced from the end of the ceramic member by an annular open space, a peripheral groove in said portion of largest diameter adjacent said shelf whereby the width of the shelf is reduced, and flexible vacuumetight seal means for joining said metal and ceramic parts together in spaced relation comprising a. flexible sealing member having a first flange bonded to the outer surface of the ceramic member and having an inwardly directed second flange bonded to the Shelf, andoccupying only a portion of sai 8,008,603 5 6 annular open space, the second flange having a portion References Cited in the file of this patent overlying the groove, and the first flange having a portion overlying and movable into and out of said annular open UNITED STATES PATENTS space between the end of the ceramic member and the 2,650,683 McPhee Sept. 1, 1953 adjacent surface of the second flange. 5 2,880,349 Polese Mar. 31, 1959 

